1. Field of the Invention
The present invention relates to a yaw moment control system in a vehicle, in which the steering characteristic is changed by distributing different amounts of torque to left and right wheels.
2. Description of the Prior Art
There is a conventionally known yaw moment control system in a vehicle which has already been proposed by the present assignee and which is designed to control the yaw moment by generating a driving force in one of the left and right vehicle wheels which are connected to each other by a gear box and a torque transmitting clutch, and generating a braking force in the other wheel. An undesirable yaw moment generated upon acceleration or deceleration of the vehicle when it is being turned, is eliminated by setting the distribution amounts of the driving force and the braking force as a function of a product of the longitudinal acceleration and the lateral acceleration (see Japanese Patent Application Laid-open No. 9-86203).
In the above known system, the stability during traveling of the vehicle particularly at a high speed is enhanced by distributing the driving force to an inner wheel during turning of the vehicle and distributing the braking force to an outer wheel during turning of the vehicle in order to eliminate an over-steering tendency generated during deceleration of the vehicle. It is possible to enhance the stability in the deceleration of the vehicle during traveling thereof at a high speed by the above-described control. However, if the same control is carried out in the deceleration of the vehicle during traveling thereof at a low speed, there is a possibility of an under-steering tendency is increased by the excessive control to provide a sense of incompatibility to a driver.
In the above known system, an output signal from a lateral acceleration sensor and an output signal from a steering angle sensor are used for calculating a lateral acceleration. However, when the vehicle is decelerating, a driver may perform a counter-steering in some cases and hence, if the output signal from the steering angle sensor is used during deceleration of the vehicle, there is a possibility that the actual direction of turning of the vehicle and the output signal from the steering angle sensor do not correspond to each other.